Dietary restriction increases variability in longevity.

Nutritional environments, particularly those experienced during early life, are hypothesized to affect longevity. A recent cross-taxa meta-analysis found that, depending upon circumstance, average longevity may be increased or decreased by early-life dietary restriction. Unstudied are the effects of diet during development on among-individual variance in longevity. Here, we address this issue using emerging methods for meta-analysis of variance. We found that, in general, standard deviation (s.d.) in longevity is around 8% higher under early-life dietary restriction than a standard diet. The effects became especially profound when dietary insults were experienced prenatally (s.d. increased by 29%) and/or extended into adulthood (s.d. increased by 36.6%). Early-life dietary restriction may generate variance in longevity as a result of increased variance in resource acquisition or allocation, but the mechanisms underlying these largely overlooked patterns clearly warrant elucidation.

Sex in unisexual salamanders: discovery of a new sperm donor with ancient affinities.

Although bisexual reproduction has considerable evolutionary benefits, several all-female vertebrates exist. Unisexual salamanders in the genus Ambystoma are common around the Great Lakes region in eastern North America. They originated from a hybridization event that involved a female that shared a common ancestor with Ambystoma barbouri 2.4 to 3.9 million years ago but, unexpectedly, A. barbouri nuclear genomes were unknown in unisexuals. Unisexual salamanders steal sperm from donors of normally bisexual species, so their reproductive mode is described as kleptogenesis. Most known unisexuals are polyploid and they all possess at least one A. laterale genome. One or more other genomes are taken from sperm donors that may include A. jeffersonianum, A. laterale, A. texanum and A. tigrinum. We examined unisexual adults and larvae in a southern Ohio pond where unisexual individuals coexist with male A. barbouri. This population provided an opportunity to test hypotheses pertaining to the role of A. barbouri in the evolution of the disparate cytoplasmic and nuclear genomes in unisexual salamanders. Microsatellite DNA loci, mitochondrial DNA sequences and genomic in situ hybridization were used to identify the genomic constitution of individuals. A. barbouri was found to be an acceptable sperm donor for unisexuals but only contributed genomes in ploidy-elevated individuals. In the absence of A. jeffersonianum, this Ohio population is likely experiencing a recent switch in sperm donors from A. jeffersonianum to A. barbouri and demonstrates the evolutionary flexibility and dynamics of kleptogenesis.